but they did not think of any method by which their suppositions could be brought to the test of experiment. The remarks of the abbé Nollet on this subject, considering the time at which they were made, are so striking, that we consider them well deserving of a place in the memory of every lover of the electrical science, and shall here record them.

18. If,' says he, 'any one should take upon him to prove from a well connected comparison of phenomena, that thunder is in the hands of nature what electricity is in ours; that the wonders which we now exhibit at our pleasure, are little imitations of those great effects that frighten us, and that the whole depends upon the same mechanism: if it can be demonstrated that a cloud prepared by the action of the winds, by heat, by a mixture of exhalations, &c., is opposite to a terrestrial object; that this is the electrified body, and at a certain proximity to that which is not; I avow that this idea, if it were well supported, would give me a great deal of pleasure; and, in support of it, how many specious reasons present themselves to a man who is well acquainted with electricity! The universality of the electric matter, the readiness of its action, its inflammability, and its activity in giving fire to other bodies, its property of striking externally and internally even to their smallest parts, the remarkable example we have of this effect in the Leyden experiment, the idea which we might truly adopt in supposing a greater degree of electric power, &c.; all these points of analogy, which I have been some time meditating, begin to make me believe, that, by taking electricity for the model, one might form to one's self, in respect to thunder and lightning, more perfect and more probable ideas than have hitherto been offered.'

19. It is generally admitted that the French philosophers were the first to verify these conjectures; they preceded the justly celebrated Dr. Franklin in drawing the electric matter from the clouds by means of an iron conducting rod; but, within a month after they had done so, the American philosopher effected the same thing in a manner that never seems to have entered into their minds. Speaking of the observations of the abbé Nollet, above quoted, Mr. Singer justly remarks, that thy bear no comparison with the acute conception, sound philosophical argument, and satisfactory experiments, by which Dr. Franklin has demonstrated the identity of the electric fluid, and the cause of thunder. Dr. Franklin, says he, had observed with equal attention the peculiarities of the natural phenomenon, and the power to which he ascribed its production; he enumerated the following as their leading features of resemblance:

(1.) The zigzag form of lightning corresponds exactly in appearance with an electric spark that passes through a considerable interval of

air.

(2.) Lightning most frequently strikes such objects as are high and prominent, in preference to others, as the summits of hills, the masts of ships, high trees, towers, spires, &c. The electric fluid, when striking from one body to another, always passes through the most prominent parts.

(3.) Lightning is observed to strike most frequently into those substances that are good conductors of electricity, such as metals, water, and moist substances; and to avoid those that are non-conductors.

(4.) Lightnings inflame combustible bodies. The same is effected by electricity.

(5.) Metals are melted by a powerful charge of electricity. This phenomenon is one of the most common effects of a stroke of lightning.

(6.) The same may be observed of the fracture of brittle bodies, and of other expansive effects common to both causes.

(7.) Lightning has often been known to strike people blind. Dr. Franklin found, that the same effect is produced on animals when they are subject to a strong electric charge. (8.) Lightning destroys animal life. Dr. Franklin killed turkies of about ten pounds weight, by a powerful electric shock.

(9.) The magnetic needle is affected in the same manner by lightning and by electricity, and iron may be rendered magnetic by both

causes.

The phenomena are therefore strictly analogous, and differ only in degree; but if an electrified gun-barrel will give a spark, and produce a loud report at two inches distance, what effect may not be expected from perhaps 10,000 acres of electrified cloud? And is not the different extent of these conductors, equal to the different limit of their effects? But to ascertain the accuracy of these ideas, let us have recourse to experiment.

Pointed bodies receive and transmit electricity with facility; let, therefore, a pointed metal rod be elevated in the atmosphere, and insulated; if lightning is caused by the electricity of the clouds, such an insulated rod will be electrified whenever a cloud passes over it, and this electricity may then be compared with that obtained in our experiments. Such were the suggestions of this admirable philosopher: they soon excited the attention of the electricians of Europe, and having attracted the notice of the king of France, the approbation he expressed excited in several members of the French Academy a desire to perform the experiment proposed by Franklin, and several insulated and pointed metallic rods were erected for that purpose.

20. In this pursuit the most active persons were two French gentlemen, Messrs. D'Àlibard and Delar. The former prepared his apparatus at Marly la Ville, five or six leagues from Paris; the latter at his own house, on some of the highest ground in that capital. M. D'Alibard's machine consisted of an iron rod forty feet long, the lower extremity of which was brought into a sentry-box, where the rain could not come; while on the outside it was fastened to three wooden posts by long silken strings defended from the rain. This machine was the first that was favored with a visit of the etherial fire. M. D'Alibard himself was not at home; but, in his absence, he had entrusted the care of his apparatus to one Coissier, a joiner, who had served fourteen years in the army, and on whose courage and understanding he could depend. This artisan had all the necessary instructions given him; and was desired to call some of his,

endeavoured to recover life by violent friction, but in vain. There appeared a red spot on the forehead, from which spirted some drops of blood through the pores, without wounding the skin. The shoe belonging to the left foot was burst open, and uncovering the foot at that part, they found a blue mark; whence it was concluded, that the electric matter having entered at the head, made its way out again at that foot. Upon the body, particularly on the left side, were several red and blue spots resembling leather shrunk by being burnt. Many more also became visible over the whole body, and particularly over the back. That upon the forehead changed to a brownish red, but the hair of the head was not singed. In the place where the shoe was burst, the stocking was entire; as was the coat every where, the waistcoat only being singed on the fore flap: but there appeared on the back of Mr. Solokow's coat long narrow streaks, which probably arose from fragments of the red hot wires falling on it and burning off the nap. Next day, when the body was opened, the cranium was very entire, having neither fissure nor contra-fissure: the brain was sound; but the transparent pellicles of the windpipe were excessively tender, and easily rent. There was some extravasated blood in it, as also in the cavities below the lungs. Those of the breast were quite sound; but those towards the back of a brownish black color, and filled with more of the blood above-mentioned. The throat, the glands, and the small intestines, were all inflamed. The singed leather-colored spots penetrated the skin only. In forty-eight hours the body was so much corrupted that they could with difficulty place it in the coffin. It is said that, at the time of his death, professor Richman had in his pocket seventy rubles of silver, which were not in the least affected by the lightning.

25. There was no longer any doubt remaining as to the identity of lightning, and the electricity produced by the electrical machine; and the great practical use made of this discocovery was to secure buildings, ships, &c., from being damaged by lightning, by erecting on them pointed metallic rods, rising a little above the highest part of the building, and passing along it so as to communicate with the ground or the nearest water, a full account of which will be given in the course of this essay.

26. A short time previous to the event of professor Richman's death, a most remarkable attempt was made by a gentleman in Italy, to gain on the credulity of his countrymen and others, by pretending that if odoriferous substances were enclosed in glass tubes, and the tubes excited, the medicinal virtues of those substances would transpire through the glass, impregnate the atmosphere of the conductor, and thus be readily communicated to the patient without being taken into the stomach. The most astonishing cures were said to have been performed by these medicated tubes; and the inventor, J. Francisco Pivati, published an account of them to the world. Both the British and French philosophers united in investigating the merits of Pivati's experiments, and the result was a complete failure, in every inVOL. VIII.

stance in which the experiments were repeated, though this was done in the presence of those who pretended to have been so successful; and, in some cases, with the very apparatus they themselves had used. The theory was, consequently, no longer credited.

27. To enumerate, in chronological order, all the discoveries that have been made in the science of electricity, from the invention of the Leyden phial to the present period, would swell this introductory sketch far beyond its proper limits; and yet, as having so eminently contributed towards raising the science to its present elegant, improved, and highly prosperous state, there are several whose names it would be injustice to pass by in silence. As the chief of these we may notice the following: Mr. Canton, an eminent English electrician, who distinguished himself by a very successful repetition of Dr. Franklin's experiments on atmospherical electricity; a method of electrifying the air of a room, either positively or negatively; and particularly by disproving the correctness of the theory of vitreous and resinous electricity, and showing that every electric is capable of giving it both in a positive and negative form, according to the nature of the surface of the body, and the kind of rubber with which it is excited.

This ingenious electrician made several remarkably fine experiments on electrical atmospheres, which led to the establishment of the fact, that bodies immersed in them became possessed of the electricity the opposite of that of the body into the atmosphere of which they are placed.

28. In connexion with the name of Canton must be mentioned that of Beccaria, author of a work entitled Dell' Elettricismo Artificiale e Naturale, and which was translated into English in the year 1776. The discoveries of Signor Beccaria were nearly the same as those of his contemporary, Mr. Canton, although they had had no communication with each other on the subject. Beccaria also made some very important experiments on the conducting power of water; in these he ascertained, that water is a very imperfect conductor of electricity; that it conducts it according to its quantity, and that, when used in very small quantities, its resistance was greatest. See BECCARIA.

29. Some interesting discoveries were made in the year 1759, on the electrical qualities of silk, by Mr. Symner. An account of these he published in the Philosophical Transactions. His attention seems to have been directed to the subject by accidentally observing, that, on pul ling off his silk stockings in the evening, a crackling noise proceeded from them, and that in the dark they emitted sparks of fire. He found that these electrical appearances were always the strongest when a silk and worsted stocking were both on one leg, and that it was of no consequence which of them was next the skin, but that they must be of different colors, one white and the other black. Two stockings of this description, worn on the leg for the short space of ten minutes, on being pulled off, stood inflated as if the leg had been within them, and, on being drawn asunder, attracted each other at

C

the distance of eighteen inches. These effects are always most powerful when the stockings are new, or when newly washed. Those who choose to try this very simple experiment will find it succeed equally well if the stockings are placed one within the other, drawn a few times through the hand, and then quickly pulled asunder.

30. Mr. Kinnersly, an intimate friend of Dr. Franklin, made several experiments that contributed to the advancement of electricity. These related chiefly to the discovery of the two electricities, the conducting power of water at different temperatures, and the power of strong charges of electricity when passed through brass wires. In the first of these experiments he had been anticipated by M. Du Fay; but he soon perceived that Du Fay did not consider the two electricities in the same light as that in which they were viewed by Franklin, viz. positive and negative.

31. In 1757 a work appeared on electricity, entitled Disputatio Physica Experimentalis de Electricitatibus, by Mr. Wilke, of Rostock, in Lower Saxony, in which the author gives some very interesting details of his researches respecting the electricity developed during the melting and cooling of electrical substances, and also that produced by the friction of different bodies. This gentleman found that, when sulphur is melted in an earthen vessel placed upon conductors of electricity, it is strongly electrified when taken out after it is cold; but that it shows no signs of electricity if cooled upon electrics. Melted sealing-wax, he found, acquired negative electricity when poured into glass vessels, but positive electricity when poured into sulphur. Mr. Wilke also confirmed the experiments of Dr. Franklin and Mr. Canton on electrical atmospheres, and illustrated the phenomena of electrical light.

32. M. Alpinus, a member of the Imperial Academy at St. Petersburgh, seems to have been the first who gave to the world a mathematical demonstration of the theory of electricity. An exposition of his treatise was published by the abbé Hauy; and an excellent paper, on the same subject, was drawn up for the Royal Society by Mr. Cavendish, before he knew any thing of the theory of M. Alpinus. The merits of M. Alpinus are certainly great, but we consider Cavendish as having much higher claims as an electrician; his experiments on the conducting power of water and wire; his very ingenious construction of the artificial torpedo; and above all, his success in employing electricity as a chemical agent, justify this opinion. 33. The labors of Dr. Priestley, as an electrician, are deservedly held in the highest esteem; the doctor brought no common share of ingenuity and perseverance to bear upon the science; and to him we are indebted for a considerable number of important improvements and interesting experiments in electricity, as connected with chemistry; for a most excellent treatise on the History of Electricity; an Introduction to Electricity; several valuable papers on the same subject, inserted in the Philosophical Transactions; and for numerous improvements in the construction of electrical apparatus.

34. The theories of Alpinus and Cavendish were much improved on by the ingenuity of M. Coulomb. By those philosophers the action of the electric matter, in producing attraction or repulsion, was considered merely as diminishing with the distance; but by the experiments of Coulomb it was proved that the electrical force, like that of gravity, is in the inverse ratio of the squares of the distance. The instrument with which Coulomb made his experiments was of his own construction: he gave it the name of the torsion balance,' from the manner of its action; a description of it will be given in the course of this essay. Coulomb also made numerous experiments for the purpose of ascertaining the laws by which the dissipation of the electrical matter in the air is regulated; and also to ascertain the distribution of it in an overcharged body. In prosecuting these enquiries he was certainly as successful as could possibly be expected, considering the extreme delicacy of his apparatus, and the effects which the variableness of the atmosphere produces on the strongest electrical experiments.

35. To M. De Saussure we are also indebted for some remarkably fine experiments, which seem to have been made with great care, on the electricity developed during the conversion of fluids into vapor. The fluids on which he operated were distilled water, spirit of wine, and ether. The same philosopher likewise made some highly interesting experiments on atmospherical electricity, for the verification of which he made a journey to the Alps.

36. Most of those who have devoted the attention to the study of electricity, as a science, have distinguished themselves by the invention of some new instrument, the use of which has generally led to some important discovery.

This was peculiarly the case with Sig. Volta, professor of natural philosophy at Como in Italy. He invented the electrophorus, an ingeniously constructed instrument for collecting and retaining the electric matter; and another called a condenser, the use of which is to accumulate, and render visible, the smallest portions of electricity, natural or artificial. The celebrity of Volta, however, rests chiefly on the important improvements which he made in that branch of electricity designated GALVANISM, under which they will be fully considered.

37. We have already noticed the scientific experiments of Coulomb, and must here observe that Dr. Robison, late professor of natural philosophy in the university of Edinburgh, is justly entitled to a share of the honor bestowed on Coulomb, since he had, so early as the year 1769, made numerous and remarkably successful attempts, with an admirable electrometer of his own invention, to determine the laws of electric action. But the professor did not publish an account of his experiments at the time they were made, which certainly gives them the appearance of posteriority. The conclusion to which Dr. Robison's experiments led him was, that the force of electrical attraction and repulsion is nearly in the inverse ratio of the square of the distance. The specific result,' says Dr. Brewster, 'which he obtained was, that the mutual repulsion of

ried as 2 ď.06 their centres.'

38. As electricity now began to be more generally cultivated, it was to be expected that great improvements in the construction of apparatus would take place. This was the case; and the brilliant success of Van Marum of Haarlem, in experiments which had failed in the hands of others, was obviously owing to the prodigious power of the large apparatus constructed by Mr. Cuthbertson of London, and placed in Tyler's

museum at Haarlem. Some notice of these ex

periments will be taken in the course of this article; at present it may be sufficient to state, that, whatever other philosophical instrument makers may have conceived, Mr. Cuthbertson has brought forth the most useful, because the most powerful, electrical apparatus with which we are yet acquainted.

39. Mr. Cavallo is justly entitled to respectful notice in every historical sketch of the rise and progress of the electrical science, to which he made many important additions. This philosopher made numerous experiments on atmospherical electricity; and also added to our stock of electrical apparatus, by his invention of the most ingeniously constructed instruments for measuring, doubling, condensing, and multiplying electricity.

40. There are other philosophers who have liberally contributed to the progressive improve ment of this branch of natural philosophy, on whose merits we cannot here dwell; but this we the less regret as their improvements and discoveries must be still fresh in the memory of those who feel an interest in the science, Among these we would simply enumerate the ingenious and laborious Nicholson, the venerable M. Hauy, Mr. Brooks, Mr. Bennet, Mr. Henley, Mr. Morgan, La Place, and the truly ingenious annalist M. Poisson.

of their labors.

40. Many other names of deserved celebrity might be here mentioned, as having successfully labored in raising electricity to its present eminent station among the sciences; but we must bring this part of our article to a conclusion by acknowledging our obligations to them, and intimating that we shall occasionally avail ourselves This remark is meant to apply particularly to the excellent treatise on electricity by the late Mr. George John Singer, a popular lecturer on this science. Mr. Singer's name stands high in the scientific world; and competent judges have pronounced his Elements of Electricity and Electro-Chemistry one of the best and most original works on the subject in the English language

PART I.

ON THE PHENOMENA OF EXCITED ELECTRICITY.

41. The more simple methods of exciting electrics enable us to perform several pleasing and instructive experiments, without the aid of costly and complex apparatus; the principal of these we now proceed to describe.

If two silk ribands, the one black and the other white, about two or three feet in length, and perfectly dry, be applied to each other by their surfaces, and then drawn smartly a few times bevelvet or woollen cloth, they will be found to tween the finger and thumb, or over dry silk adhere to each other with considerable force; and when separated at one end will rush together again with rapidity. Each riband, when separated, will attract any light substances to which it is presented; and, if the experiment be made in a dark room, a flash of light will occasionally attend the separation of the ribands.

42. Sticks of sealing-wax, resin, or sulphur, when rubbed with dry woollen cloth, or fur; and tubes or rods of glass, when rubbed with silk, exhibit similar powers; and, if of sufficient size, produce, when applied within a short distance of the face or hand, a distinct and singular sensation. These effects having been first produced by the friction of amber (electron) are called electrical phenomena; and the processes employed for their production, the excitation of electricity.

43. Attraction is the phenomenon most constantly attendant on excitation; it is therefore considered as an indication of the presence and action of electricity, and is the basis of all its tests. Electricians formerly, says Mr. Singer, employed for such trials a light wooden or metal needle, supported by its centre on a point, or a thread or feather delicately suspended. To these attracted by it, the attraction was attributed to electhe excited body was presented, and, if they were tricity, and the excited body was called an electric.

44. This suspended needle, and every other contrivance for the same purpose, they called an electroscope, when employed to indicate the existence of electricity; and an electrometer when considered as a measure of its force; but the contrivance hitherto employed to ascertain the latter term appears fully sufficient, since every presence of electrical phenomena is also calcuelectrometers, for common purposes, are conlated to measure their power. The most useful structed by suspending two narrow slips of gold leaf from the cap of a glass cylinder. When these are unelectrified they will hang parallel and contiguous; the presence of the smallest quantity of electricity will cause them to diverge towards the sides of the cylinder.

Small balls turned from the pith of elder, and suspended by fine threads or silver wires, are sometimes substituted for the gold strips. They are less easily affected, but they are more durable. The pith balls, suspended by thread or wire, are also occasionally used without a glass cylinder. But these and other electrometers will be explained hereafter..

45. Electrical phenomena are thus characterised by the attraction and recession of light substances; the consequent production of motion in them, and of sensation in living bodies, and by the evolution or production of light. There are various methods by which these effects may be produced, but the following are the most obvious sources of their production. (1.) Friction. (2.) Change of form. (3.) Change of temperature. (4.) Contact of dissimilar bodies.